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Test-Retest Reliability of Low-Cost Posturography for Assessing Postural Stability Control Performance during Standing

Test-Retest Reliability of Low-Cost Posturography for Assessing Postural Stability Control... Hindawi Journal of Aging Research Volume 2021, Article ID 9233453, 11 pages https://doi.org/10.1155/2021/9233453 Research Article Test-Retest Reliability of Low-Cost Posturography for Assessing Postural Stability Control Performance during Standing 1 2 Sumet Heamawatanachai , Witawit Wiriyasakunphan , 2 2 Kanokwan Srisupornkornkool , and Chaiyong Jorrakate Faculty of Engineering, Naresuan University, Phitsanulok 65000, ailand Faculty of Allied Health Sciences, Naresuan University, Phitsanulok 65000, ailand Correspondence should be addressed to Chaiyong Jorrakate; chaiyongj@nu.ac.th Received 10 May 2021; Accepted 27 July 2021; Published 5 August 2021 Academic Editor: Carmela R. Balistreri Copyright © 2021 Sumet Heamawatanachai et al. )is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Postural stability control performance assessment is necessary in providing important information for individuals who are at risk of falling or who have balance impairment. Instrumented assessment is suggested as a valid and reliable test, but the cost and the difficulty of setup are significant limitations. )e aim of this cross-sectional (test-retest reliability) study was to develop and determine the reliability of a low-cost posturography for assessing postural stability control performance during standing. )e low-cost posturography was developed with four load cells and an acrylic platform. )e center of pressure (COP) displacement and velocity were analyzed using written software. Test-retest reliability was performed with six different standing postural stability tests in twenty healthy volunteers on two different days. Intraclass correlation coefficient (ICC), standard error of measurement (SEM), coefficient of variation (CV), and Bland–Altman plot and limits of agreements (LOA) were used for analyses. )e low-cost posturography was accurate (ICC � 0.99, p< 0.001; SEM � 0.003 cm) when compared to the true with calculated X and Y coordinates, with a moderate to excellent test-retest reliability for both COP displacement (ICCs ranged 0.62–0.91, p< 0.05; SEMs ranged 17.92–25.77%) and COP velocity (ICCs ranged 0.62–0.91, p< 0.05; SEMs ranged 18.09–27.69%) in all standing postural stability tests. Bland–Altman plots and LOAs suggested good agreement of tested parameters from the developed low-cost posturography between different days. In conclusion, the developed low-cost posturography had adequate reliability for assessing COP displacement and velocity during standing postural control stability performance tests. with a huge cost to healthcare services, wasted time, loss of 1.Introduction opportunities and a poor quality of life [5, 6]. Problems with Postural control is an essential component of the motor control postural stability control are commonly found across a variety needed to achieve a body motion oriented to daily living en- of age ranges, including children and adolescents [7, 8], adults vironments [1, 2]. Postural control is governed by the central [9] and the elderly [10, 11]. Exercise interventions have been nervous system in order to purposefully accomplish target utilized and suggested as an effective strategy to recover postural stability control performance [12–14]. Besides ef- movements [2]. Postural control consists of two major com- ponents, including postural stability control (both static and fective treatment, the assessment of postural stability control dynamic movements) and postural equilibrium control [3, 4]. performance is also important, as it helps the clinician to Postural stability control performance during static standing is a monitor the progression of treatment and to establish an fundamental capability of humans, achieved by stabilizing appropriate goal for postural stability control rehabilitation the core of the body to efficiently move peripheral extremities. [15, 16]. Additionally, postural stability control assessments Impairment of postural stability control not only causes are suggested to be routinely applied to screen the elderly for ineffective motion but also leads people to become a burden; early detection of a risk of falling [17]. 2 Journal of Aging Research Instrumented postural stability testing has been widely power and ICC � 0.6) [28]. Healthy young adult volunteers used for assessing postural stability control performance (10 male and 10 female) aged 10–25 years old with no history [15]. Instrumented testing with a force platform, postur- of back and lower extremity arching and no musculoskeletal ography, and stabilography are frequently provided to assess and neurological problems were recruited. Volunteers with postural stability control performance. With those instru- apparent standing balance disturbance, other problems re- mented tests, the center of pressure (COP) is a quantitative lated to postural control disability, a history of recurrent parameter which is usually used to quantify postural stability ankle sprain, a history of serious traumatic injury to the back control performance [18, 19]. )e subparameters of the COP and lower extremities, and undertaking any exercise or usually reported in previous studies include position of the sports training programs were excluded. All volunteers were COP, root mean square (RMS) amplitude of the COP, total asked not to sleep less than 6 hours per night and not to use excursion of the COP, sway velocity of the COP, and sway medications or consume alcohol which would affect postural area of the COP. )e COP displacement (or the COP path stability control performance prior to participating in this length) and the COP velocity were suggested to be reliable study. In female volunteers, testing procedures were not conducted during their menstruation period or during and valid measures for determining postural stability control performance during standing [15, 18–21]. However, so- pregnancy. phisticated postural stability assessment instruments are high in cost, complexity, and time-consumption related to settings. Furthermore, most of them were often furnished in 2.2. Instruments and System Overview. )e SBAP (Figure 1) consisted of an acrylic platform (50 cm width x 50 cm research areas and could not be made easily accessible. )erefore, a number of studies have focused on developing length x 0.5 cm thickness) with four parallel beam load cells (each of 100 kg rated capacity, OEM) embedded under the accurate and reliable tools for determining postural stability control performance with lower cost equipment [22, 23]. In four corners of platform. )e load cells were connected with signal amplifiers (model Hx711) and a microcontroller the last decade, several studies demonstrated that a Wii TM Balance Board (WBB) with developed software was a (Arduino Uno). )e acrylic platform was mounted on an aluminium frame (50 cm width x 50 cm length x 15 cm valid and reliable tool for a low-cost postural stability control height) which was glued to a nonslip material on the bottom performance assessment [20, 22, 24–27]. )e WBB seemed surface. )e SBAP was interfaced with a laptop computer to be a suitable choice; however, the developed software (Lenovo Intel from previous studies is not widely disseminated. In addi- Core i5-8250U, CPU 1.6 GHz) via a USB tion, the cost of the WBB is quite high and is generally cable connector. )e weight of SBAP was approximately 7 kg. considered to be inaccessible in clinical settings and to the low-income population. )erefore, the current study aimed )e custom-made software for calculating the COP displacement and velocity was developed and written in to report the development of a low-cost, accurate, and re- liable posturography, evaluating COP time-domain pa- LabVIEW. )e COP displacement was referred to as a whole distance of the COP over the test duration (unit of mea- rameters. It was hypothesized that the developed posturography would display accurate measurement and surement: centimeter, cm). )e COP velocity was derived from the COP displacement over time (unit of measure- reliable test-retest reliability. )is low-cost posturography could offer easier access and more user friendly use in ment: centimeter per second; cm/second). )e signals from clinical settings. the four parallel beam load cells were delivered and con- verted to digital information by the written software. )e sampling frequency was recruited at 10 Hz by the software 2.Materials and Methods with no data filtering. )e signals from the load cells were processed and computed to get the total weight press on the )e current study utilized a cross-sectional research design platform along with the COP location (in the form of X and with test-retest reliability. A low-cost posturography was Y coordinates). )e COP displacements were calculated developed as a prototype named “Standing Balance As- from the total distance of change in the COP location over sessment Posturography (SBAP).” )e SBAP was pur- the testing duration. )e COP velocities were calculated posefully used to analyze the COP time-domain parameters from the COP displacement divided by the testing duration. (COP displacement and velocity) during standing. All After clicking the start button of the developed software, testing procedures were approved by the Naresuan Uni- SBAP started recording the input information for 40 seconds versity Institutional Review Board (IRB no. P10186/63). All and then stopped automatically. )e COP parameters were volunteers signed an informed consent before participating then processed and calculated during the middle 30 seconds. in the current study. )e COP displacement, the COP velocity, and a graphical real-time COP trajectory were presented on the laptop’s screen (Figure 2). 2.1. Participants. Participants were recruited in Naresuan University area through purposive sampling, using flyers, Before conducting postural stability control perfor- mance tests with SBAP, the accuracy of SBAP was initially posters, and personal contacts. )e number of participants (20 volunteers) was determined according to a guideline for tested with a standard 5 kg weight placed sequentially in nine positions over the platform (Figure 3). )e 5 kg weight was sample size estimation for analysis with the intraclass cor- relation coefficient (ICC) (two observations per subject, 90% placed 5 times repeatedly in each position. )e actual or true Journal of Aging Research 3 Load cell 1 Load cell 2 The SBAP Load cell 4 Load cell 3 (a) (b) Figure 1: )e standing balance assessment posturography (SBAP): (a) position of load cells; (b) overview of SBAP. Figure 2: Display of the developed software with SBAP. positions on the platform and the 45 calculated positions volunteers were asked to wear a comfortable shirt, short (9 positions x 5 times) from the software were then analyzed pants, and be bare foot. To prevent falling, volunteers wore a for the accuracy of the X and Y coordinates of the system. full body harness with nylon rope slings firmly suspended from the supporting frame. All volunteers were introduced to the testing protocols and were allowed to practice until 2.3. Data Collection. After volunteers had signed an in- they became familiar with the testing procedure. formed consent, they were screened according to the in- Postural stability control performance was tested via clusion and exclusion criteria. Volunteers who passed the standing balance assessments. )e standing balance as- criteria were tested for their dominant leg by performing sessments were varied visual inputs and bases of support to three activities: kicking a ball, writing their names on the challenge postural control ability. Standing balance assess- floor, and picking up an object. )e dominant leg was ments were tested in 6 different conditions, and each identified if they used the same leg to perform at least 2 condition was performed thrice. )e COP trajectory real- activities. time display was eliminated from volunteers during the tests. All measurements were conducted at a single site, the Successful trials were affirmed when the volunteer could Faculty of Allied Health Sciences, Naresuan University, stand without swaying or falling and did not open their eyes )ailand. )e laboratory room was silent and no other during the eyes closed condition. If an unsuccessful trial activities were allowed to avoid distraction. Initially, occurred, the volunteer was asked to perform repeatedly 4 Journal of Aging Research 2.4. Statistical Analysis 2.4.1. Accuracy of SBAP. )e mean differences between the true and calculated X and Y coordinates from the nine positions over the platform (N � 45) were determined for accuracy using an intraclass correlation coefficient (two-way random, absolute agreement, single measure) [29] and a standard error of measurement (SEM). )e SEM was ana- lyzed using the equation “SEM � SD (square root of 1- ICC)” [25, 30]. 2.4.2. Test-Retest Reliability of SBAP during Postural Stability Control Performance Tests in Six Conditions. )e charac- teristics of volunteers were descriptively reported. )e mean of the COP displacements and the COP velocities during the six testing conditions in session 1 and 2 were descriptively demonstrated. Scatter plots were primarily checked for Figure 3: Nine positions and a 5 kg weight for testing SBAP linearity of COP displacements and velocities between accuracy. session 1 and 2. Afterward, test-retest reliability of the postural stability tests with SBAP were analyzed from dif- ferent days (sessions 1 and 2) using the intraclass correlation until 3 successful trials in each condition were completed. coefficient (ICC) (two-way mixed effect, consistency, aver- )e 6 different standing postural stability control perfor- age measure). )e values of the ICC were qualitatively mance test conditions were as follows (Figure 4). classified as displaying excellent (ICC >0.90), good (ICC (i) Double leg stance with feet shoulder width apart between 0.75 and 0.90), moderate (0.50–0.75), and poor and eyes open (DLS-SW-EO), arms by their sides, (ICC <0.50) reliability [31]. Additionally, a coefficient of the distance between feet was recorded variation (CV) [30] and SEM of the COP displacement and velocity in sessions 1 and 2 were also analyzed. Furthermore, (ii) Double leg stance with feet shoulder width apart Bland–Altman plots for the COP displacements and ve- and eyes closed (DLS-SW-EC), arms by their sides, locities were also graphically displayed showing the agree- the distance between feet was recorded ment and systematic bias of each measurement between (iii) Double leg stance with feet together and eyes open sessions with 95% limits of agreement (LOA). Statistical (DLS-FT-EO), arms by their sides analysis was conducted with the Statistical Package for Social (iv) Double leg stance with feet together and eyes closed Sciences (SPSS). )e p value was set at or less than 0.05 for all (DLS-FT-EC), arms by their sides statistical analyses. (v) Single leg stance with eyes open (SLS-EO), other leg bent at 90 degrees of knee flexion toward the back, 3.Results arms crossed on their chest 3.1. Volunteers. Twenty young adult volunteers (age � (vi) Single leg stance with eyes closed (SLS-EC), other 21.45± 0.59 years, weight � 53.21± 7.32, height � 165.50± leg bent at 90 degrees of knee flexion toward the 5.16 cm, and body mass index � 19.40± 2.34 kg/m ) were back, arms crossed on their chest recruited in the current study. All volunteers were com- )e testing conditions were randomly assigned for each pletely measured against the testing protocols in sessions 1 volunteer. )e volunteers were asked to stand still in the and 2. Physical and emotional changes which apparently middle of SBAP for over 40 seconds in each test. Two disturbed postural stability control performance were not minutes rest or longer was allowed between trials or until the observed in all volunteers. No falling or serious adverse volunteers had no fatigue or tiredness before starting the effects were detected throughout the study. new trial or condition. )e SBAP was set at zero shift before collecting data in each trial. All testing procedures were performed twice with identical procedures for all volunteers 3.2. Accuracy of SBAP. Means and standard deviations of the in two different sessions. )e second session was tested 24 differences between the true and calculated X and Y coor- hours after the first session. Each session took place over dinates were −0.13± 0.22 cm and −0.12± 0.17 cm, respec- approximately 45 minutes. All measurements in the two tively. )e reliability coefficients from ICC analysis were 0.99 sessions were conducted by the same tester who was ap- (95% confidence interval � 0.99–1.00, p< 0.001) for both X propriately instructed and trained in all testing protocols. )e and Y coordinates. )e SEMs of differences between true tester separately recorded and exported the testing parameters and calculated positions of X and Y coordinates were of individual volunteers after completing the testing proce- 0.022 cm and 0.017 cm, respectively. )ese results demon- dures in each session. All testing parameters were then an- strated high accuracy of SBAP to estimate the X and Y alyzed with statistical software by another researcher. coordinates on platform. Journal of Aging Research 5 (a) (b) (c) Figure 4: Standing postural stability control tests: (a) double leg stance with feet shoulder width apart, (b) double leg stance with feet together, and (c) single leg stance. 3.3. Test-Retest Reliability of the Postural Stability Control COP displacements and velocities between session 1 and 2 in six testing conditions was demonstrated via Bland–Altman Performance Test with SBAP in Six Conditions. Scatter plots of both the COP displacement and velocities in six testing plots with LOAs (Figures 7 and 8). )ere were no obvious conditions showed the linearity relationships of parameters trends or systematic bias between the measurements in all between sessions 1 and 2 (Figures 5 and 6). Means and testing conditions. standard deviations (SD) of the COP displacements and velocities in both sessions are demonstrated in Table 1. )e 4.Discussion results of the test-retest reliability of the postural stability control performance test with SBAP between sessions 1 and In the study of reliability analysis, measurement errors can 2, expressed with ICC values, are given in Table 2. )e results be attributed to three sources including rater, measuring showed moderate to high test-retest reliability between instrument, and variability of the characteristics being sessions 1 and 2 in the six different conditions. A moderate measured [31]. Measurement errors were minimized by test-retest reliability was found with the COP displacement suitably designing the testing procedures and protocols. All and velocity in the double leg stance with feet shoulder width measurements of testing protocols in the two sessions were apart and eyes open condition. A good test-retest reliability conducted by the same well-trained tester with a clear was identified with the COP displacements and velocities in procedure of testing protocols in order to control the the double leg stance with feet shoulder width apart and eyes measurement error from the rater. )e tested parameters of closed, double leg stance with feet together and eyes closed, individual volunteers were separately processed and and single leg stance with eyes open conditions. An excellent exported after completing each session. Afterward, the tested reliability was expressed with the COP displacement and parameters were analyzed by another researcher to reduce velocity in the double leg stance with feet together and eyes the rater’s bias on data analyses. For eliminating the mea- open and single leg stance with eyes closed conditions. surement error from measuring instrument, the low-cost )e CV and SEM of the COP displacements and ve- posturography (SBAP) was initially tested for its accuracy by locities in both sessions during the 6 testing conditions are analyzing the differences between true and calculated X and reported in Table 3. In both sessions, the CV of the COP Y coordinates before testing test-retest reliability in the displacements ranged 17.92–25.77%, whereas the CV of the young adult volunteers. )e results of this study demon- COP velocities ranged 18.09–27.69%. In each testing con- strated that SBAP had excellent precision of calculated X, Y dition, consistent CV values were observed between sessions coordinates (ICC � 0.99, SEM <0.03 cm) when compared 1 and 2 for both the COP displacement and velocity. with the true positions on the platform. )e protocols for )e SEM values were increased according to the level of postural control performance testing were appropriately difficulty of the testing conditions (from the easiest, con- designed as recommend by previous studies, including foot dition 1, to the hardest, condition 6). Again, the SEM values and leg positions, testing duration, repetitions of testing, were consistently observed between sessions 1 and 2 for both visual acuity conditions, and random-order of the testing the COP displacement and velocity. )e agreement of the conditions [15, 18, 32, 33], in order to control the variability 6 Journal of Aging Research cm cm 40 50 cm cm 0 0 0 5 10152025 0152 10 5 20530 COP displacement in session 1 COP displacement in session 1 (a) (b) cm cm 50 100 30 60 20 40 10 20 cm cm 0 0 0 10 203040 0 10 2030405060 COP displacement in session 1 COP displacement in session 1 (c) (d) cm cm 100 250 80 200 60 150 40 100 20 50 cm cm 0 0 0 20 40 60 80 100 0 50 100 150 200 250 COP displacement in session 1 COP displacement in session 1 (e) (f) Figure 5: Scatter plots of COP displacements between sessions 1 and 2 from six testing conditions. (a) COP displacements during DLS-SW- EO. (b) COP displacements during DLS-SW-EC. (c) COP displacements during DLS-FT-EO. (d) COP displacements during DLS-FT-EC. (e) COP displacements during SLS-EO. (f) COP displacements during SLS-EC. between sessions. Hence, the results of reliability analyses according to the difficulty of the tests, from the wider base of support (BOS) with the presence of visual input to the will mostly reflect the consistency of the postural stability control performance testing with SBAP. steeper BOS and the absence of visual input. It was suggested In the current study, only one group of volunteers was that as the COP displacement and velocity increased, more measured twice for COP displacements and velocities. postural stability was needed during quiet standing [21]. Young healthy adult volunteers who had no significant However, this concept might not be implied for all situa- physical factors affecting postural stability control perfor- tions. Palmieri and colleagues [18] elucidated that COP mance were recruited (both males and females in equal displacement and velocity alone might not adequately ex- number). All volunteers were asked to sleep sufficiently and plain the nature of postural stability control. )erefore, other not to use medications or alcohol which would affect pos- parameters of the COP domain should be considered for postural stability control. Additionally, various factors af- tural stability control prior to joining the testing protocols throughout the study. )e interval durations between ses- fected the characteristics of postural stability control, such as sions 1 and 2 of all volunteers were approximately 24-hour testing conditions, testing protocol, assessment tools, and apart. Female volunteers were not tested if they were in the characteristics of subjects. As mentioned, the COP dis- menstruation period or pregnant. As mentioned above, the placement and velocity may be better appropriated for in- variability of the measurement scores caused by being tested dividual longitudinal monitoring. participants would be probably controlled. )e gradual increases of the standard deviations of COP From testing conditions 1−6, the values of the COP displacements and velocities were similarly observed in both displacement were gradually increased. )ese increasing sessions. )is implies that the variability of the COP dis- values were also observed with the values of the COP ve- placements and velocities increases as the difficulty of testing locity. )e testing conditions were purposefully ranked protocols increases (from testing conditions 1–6). However, COP displacement COP displacement COP displacement in session 2 in session 2 in session 2 COP displacement COP displacement COP displacement in session 2 in session 2 in session 2 Journal of Aging Research 7 cm cm 1.4 1.2 1.5 0.8 0.6 0.4 0.5 0.2 cm cm 0 0 0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 0.8 1 COP velocity in session 1 COP velocity in session 1 (a) (b) cm cm 2 3 2.5 1.5 1 1.5 0.5 0.5 cm cm 0 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 0.5 1 1.5 2 COP velocity in session 1 COP velocity in session 1 (c) (d) cm cm 4 8 3.5 7 3 6 2.5 5 2 4 1.5 1 2 0.5 1 cm cm 0 0 0 2 46 8 0 0.5 1 1.5 2 2.5 3 3.5 COP velocity in session 1 COP velocity in session 1 (e) (f) Figure 6: Scatter plots of COP velocities between sessions 1 and 2 from six testing conditions. (a) COP velocity during DLS-SW-EO. (b) COP velocity during DLS-SW-EC. (c) COP velocity during DLS-FT-EO. (d) COP velocity during DLS-FT-EC. (e) COP velocity during SLS-EO. (f ) COP velocity during SLS-EC. Table 1: Means and standard deviations of COP displacements and velocities of six conditions in sessions 1 and 2. COP displacements COP velocities Conditions Session 1 Session 2 Session 1 Session 2 (cm) (cm) (cm/second) (cm/second) Double leg stance with feet shoulder width apart and eyes open 15.06± 3.42 15.04± 3.33 0.50± 0.11 0.50± 0.11 Double leg stance with feet shoulder width apart and eyes closed 18.21± 3.73 19.54± 3.98 0.61± 0.12 0.65± 0.13 Double leg stance with feet together and eyes open 25.18± 5.56 24.49± 4.86 0.84± 0.19 0.82± 0.16 Double leg stance with feet together and eyes closed 38.01± 8.29 39.43± 10.16 1.27± 0.28 1.30± 0.36 Single leg stance with eyes open 58.39± 13.55 56.31± 10.09 1.95± 0.45 1.88± 0.34 Single leg stance with eyes closed 132.21± 28.39 134.17± 29.23 4.41± 0.95 4.47± 0.97 most values of CVs of COP displacements and velocities in all testing conditions for both the COP displacement and all testing conditions and sessions seem to be consistent velocity was good, as demonstrated in the Bland–Altman across testing conditions and sessions (most of CV values plots and LOAs. Most differences between the 2 sessions of were 20–30%). )erefore, it could be stated that the in- COP measurement with SBAP were within ±2 SD of the creased variability observed depended on the inherent dif- mean differences in both positive and negative directions. ficulty of the testing conditions. )e test-retest reliabilities of )is indicated no significant bias between the measurements static postural control tests for both the COP displacement with SBAP from different sessions. Additionally, the values and velocity of SBAP were moderate to excellent. )e SEM of the average COP displacement and velocity were con- values of all measurements in this study were acceptable (less sistent between sessions and was in a similar range to those than 30%) [19, 32]. )e agreement between measurements in from studies which evaluated the postural control COP velocity in session 2 COP velocity in session 2 COP velocity in session 2 COP velocity in session 2 COP velocity in session 2 COP velocity in session 2 8 Journal of Aging Research Table 2: Results of test-retest reliability (intraclass correlation coefficients) for COP displacements and velocities between sessions 1 and 2 in six conditions. COP displacements COP velocities Conditions Reliability coefficients Reliability coefficients P value P value (95% confidence interval) (95% confidence interval) Double leg stance with feet shoulder ∗ ∗ 0.62 (0.05, 0.85) 0.02 0.62 (0.05, 0.85) 0.02 width apart and eyes open Double leg stance with feet shoulder ∗ ∗ 0.85 (0.61, 0.94) <0.001 0.85 (0.61, 0.94) <0.001 width apart and eyes closed Double leg stance with ∗ ∗ 0.91 (0.76, 0.96) <0.001 0.91 (0.76, 0.96) <0.001 feet together and eyes open Double leg stance with feet ∗ ∗ 0.78 (0.44, 0.91) 0.001 0.78 (0.44, 0.91) 0.001 together and eyes closed Single leg stance with ∗ ∗ 0.83 (0.56, 0.93) <0.001 0.82 (0.56, 0.93) <0.001 eyes open Single leg stance ∗ ∗ 0.91 (0.76, 0.96) <0.001 0.91 (0.76, 0.96) <0.001 with eyes closed Statistical significant at p< 0.05. Table 3: Results of coefficients of variation (CV) and standard errors of measurement (SEM) of COP displacements (cm) and COP velocities (cm/second) of six conditions in sessions 1 and 2. COP displacements COP velocities Conditions Session 1 Session 2 Session 1 Session 2 CV (%) SEM CV (%) SEM CV (%) SEM CV (%) SEM Double leg stance with feet shoulder width apart and eyes open 22.71 2.11 22.14 2.05 22.00 0.07 22.00 0.07 Double leg stance with feet shoulder width apart and eyes closed 20.48 1.44 20.37 1.54 19.67 0.05 20.00 0.05 Double leg stance with feet together and eyes open 22.08 1.67 19.84 1.46 22.62 0.06 19.51 0.05 Double leg stance with feet together and eyes closed 21.81 3.89 25.77 4.77 22.05 0.13 27.69 0.17 Single leg stance with eyes open 23.21 5.59 17.92 4.16 23.08 0.19 18.09 0.14 Single leg stance with eyes closed 21.47 8.52 21.79 8.77 21.54 0.29 21.70 0.29 performance during standing with the WBB and a labora- calculation of the written software were not precisely tory-grade force platform [16, 19, 20, 25, 34], eventhough explained. Nowadays, the WBB has decreased in popularity, there were some discrepancies in testing parameters when and eventhough the cost of the WBB has also decreased compared to this study. )erefore, it could be stated that the somewhat, its cost remains high for extensive use in clinical settings or even in home use. However, the pressure sensors developed low-cost posturography in this study had enough reliability for assessing postural stability control perfor- used in SBAP are currently decreasing in price and mance during standing. are convenient in that they can be connected to various )e instrumented test for postural stability control computer programs to effectively create the software for performance is suggested to be better than the clinical tests, biomechanical analysis. )erefore, we decided to develop a reporting more accurate and precise scores and providing low-cost posturography using simple load cells and plat- more details related to biomechanical parameters. None- form. In future developments of the system, it would be theless, the instrumented tests have rarely been used in possible to lower the cost of production and the weight of clinical settings due to their difficulty of setup, heavy weight, SBAP. and high cost. A number of studies have investigated the )e limitations of this study were related to materials reliability and validity of a low-cost posturography and external validity. )e load cells were limited to 100 kg TM loaded. )e sampling rate was low (10 Hz) with no data [16, 20, 22, 24–27]. )ey proposed the Wii Balance Board (WBB) as a low-cost posturography, which had moderate to filtering, whereas previous studies used at least 40 Hz (for the WBB) or up to 200 Hz (for a laboratory-grade force excellent reliability and good validity in comparison with a laboratory-grade force platform. However, some technical platform) with low-pass filtering (less than 10 Hz) limitations of the WBB were reported, including an in- [15, 16, 20, 22, 24–27, 32]. However, the results of the consistent sampling rate and a poor signal to noise ratio, recorded parameters still had sufficient reliability and were which may have impacted the analysis of the COP pa- consistent with previous studies [16, 19, 20, 25, 34]. Vol- rameters [22]. Consequently, several studies tried to address unteers in this study were symptom-free individuals, so the those limitations by improving the input signals with results could not be referred to another population. low-pass filtering to attenuate noise [16, 20, 22, 24–27]; In future studies, the accuracy of posturography should however, the technical details related to data acquisition and be tested with various weights and numbers of X and Y Journal of Aging Research 9 10 10 7.12 +1.96 SD 4.34 +1.96 SD 5 5 Mean difference Mean difference 0.02 0 0 0 5 101520253035 0.00 5.00 10.00 15.00 20.00 25.00 –1.33 –5 –5 –7.00 –7.07 –1.96 SD –1.96 SD –10 –10 Average COP displacements from two sessions (cm) Average COP displacements from two sessions (cm) (a) (b) 10 30 6.89 +1.96 SD 14.47 +1.96 SD 0.69 Mean difference Mean difference –1.42 0 0 0 10 20 30 40 –5 5 152535455565 –10 –5.51 –5 –20 –1.96 SD –17.31 –1.96 SD –10 –30 Average COP displacements from two sessions (cm) Average COP displacements from two sessions (cm) (c) (d) 30 50 20.64 +1.96 SD 32.13 +1.96 SD 2.07 Mean difference –1.96 Mean difference 0 20 40 60 80 100 0 5 100 150 200 250 –10 –10 –30 –16.49 –1.96 SD –20 –1.96 SD –36.06 –30 –50 Average COP displacements from two sessions (cm) Average COP displacements from two sessions (cm) (e) (f) Figure 7: Bland–Altman plots and limits of agreements (LOAs) of COP displacements in sessions 1 and 2 in six testing conditions. (a) COP displacements during DLS-SW-EO. (b) COP displacements during DLS-SW-EC. (c) COP displacements during DLS-FT-EO. (d) COP displacements during DLS-FT-EC. (e) COP displacements during SLS-EO. (f) COP displacements during SLS-EC. 0.4 0.4 0.24 +1.96 SD 0.14 0.2 0.2 +1.96 SD 0.001 Mean difference Mean difference 0 0 0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 –0.05 –0.2 –0.24 –0.2 –0.23 –1.96 SD –1.96 SD –0.4 –0.4 Average COP velocities from two sessions Average COP velocities from two sessions (cm/second) (cm/second) (a) (b) Figure 8: Continued. Differences in COP Differences in COP Differences in COP Differences in COP velocity displacement (cm) displacement (cm) displacement (cm) (cm/second) Differences in COP velocity Differences in COP Differences in COP Differences in COP (cm/second) displacement (cm) displacement (cm) displacement (cm) 10 Journal of Aging Research 0.4 1 0.23 +1.96 SD 0.52 +1.96 SD 0.2 0.5 0.02 Mean difference Mean difference –0.03 0 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 0.5 1 1.5 2 2.5 –0.58 –0.2 –0.5 –0.19 –1.96 SD –1.96 SD –0.4 –1 Average COP velocities from two sessions Average COP velocities from two sessions (cm/second) (cm/second) (c) (d) 1 2 0.69 +1.96 SD 1.07 +1.96 SD 0.5 1 0.07 Mean difference Mean difference –0.07 0 0 0 0.5 1 1.5 2 2.5 3 3.5 0 2 46 810 –0.55 –1.20 –0.5 –1 –1.96 SD –1.96 SD –1 –2 Average COP velocities from two sessions Average COP velocities from two sessions (cm/second) (cm/second) (e) (f) Figure 8: Bland–Altman plots and limits of agreements (LOAs) of COP velocities in sessions 1 and 2 in six testing conditions. 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Test-Retest Reliability of Low-Cost Posturography for Assessing Postural Stability Control Performance during Standing

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Copyright © 2021 Sumet Heamawatanachai et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Hindawi Journal of Aging Research Volume 2021, Article ID 9233453, 11 pages https://doi.org/10.1155/2021/9233453 Research Article Test-Retest Reliability of Low-Cost Posturography for Assessing Postural Stability Control Performance during Standing 1 2 Sumet Heamawatanachai , Witawit Wiriyasakunphan , 2 2 Kanokwan Srisupornkornkool , and Chaiyong Jorrakate Faculty of Engineering, Naresuan University, Phitsanulok 65000, ailand Faculty of Allied Health Sciences, Naresuan University, Phitsanulok 65000, ailand Correspondence should be addressed to Chaiyong Jorrakate; chaiyongj@nu.ac.th Received 10 May 2021; Accepted 27 July 2021; Published 5 August 2021 Academic Editor: Carmela R. Balistreri Copyright © 2021 Sumet Heamawatanachai et al. )is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Postural stability control performance assessment is necessary in providing important information for individuals who are at risk of falling or who have balance impairment. Instrumented assessment is suggested as a valid and reliable test, but the cost and the difficulty of setup are significant limitations. )e aim of this cross-sectional (test-retest reliability) study was to develop and determine the reliability of a low-cost posturography for assessing postural stability control performance during standing. )e low-cost posturography was developed with four load cells and an acrylic platform. )e center of pressure (COP) displacement and velocity were analyzed using written software. Test-retest reliability was performed with six different standing postural stability tests in twenty healthy volunteers on two different days. Intraclass correlation coefficient (ICC), standard error of measurement (SEM), coefficient of variation (CV), and Bland–Altman plot and limits of agreements (LOA) were used for analyses. )e low-cost posturography was accurate (ICC � 0.99, p< 0.001; SEM � 0.003 cm) when compared to the true with calculated X and Y coordinates, with a moderate to excellent test-retest reliability for both COP displacement (ICCs ranged 0.62–0.91, p< 0.05; SEMs ranged 17.92–25.77%) and COP velocity (ICCs ranged 0.62–0.91, p< 0.05; SEMs ranged 18.09–27.69%) in all standing postural stability tests. Bland–Altman plots and LOAs suggested good agreement of tested parameters from the developed low-cost posturography between different days. In conclusion, the developed low-cost posturography had adequate reliability for assessing COP displacement and velocity during standing postural control stability performance tests. with a huge cost to healthcare services, wasted time, loss of 1.Introduction opportunities and a poor quality of life [5, 6]. Problems with Postural control is an essential component of the motor control postural stability control are commonly found across a variety needed to achieve a body motion oriented to daily living en- of age ranges, including children and adolescents [7, 8], adults vironments [1, 2]. Postural control is governed by the central [9] and the elderly [10, 11]. Exercise interventions have been nervous system in order to purposefully accomplish target utilized and suggested as an effective strategy to recover postural stability control performance [12–14]. Besides ef- movements [2]. Postural control consists of two major com- ponents, including postural stability control (both static and fective treatment, the assessment of postural stability control dynamic movements) and postural equilibrium control [3, 4]. performance is also important, as it helps the clinician to Postural stability control performance during static standing is a monitor the progression of treatment and to establish an fundamental capability of humans, achieved by stabilizing appropriate goal for postural stability control rehabilitation the core of the body to efficiently move peripheral extremities. [15, 16]. Additionally, postural stability control assessments Impairment of postural stability control not only causes are suggested to be routinely applied to screen the elderly for ineffective motion but also leads people to become a burden; early detection of a risk of falling [17]. 2 Journal of Aging Research Instrumented postural stability testing has been widely power and ICC � 0.6) [28]. Healthy young adult volunteers used for assessing postural stability control performance (10 male and 10 female) aged 10–25 years old with no history [15]. Instrumented testing with a force platform, postur- of back and lower extremity arching and no musculoskeletal ography, and stabilography are frequently provided to assess and neurological problems were recruited. Volunteers with postural stability control performance. With those instru- apparent standing balance disturbance, other problems re- mented tests, the center of pressure (COP) is a quantitative lated to postural control disability, a history of recurrent parameter which is usually used to quantify postural stability ankle sprain, a history of serious traumatic injury to the back control performance [18, 19]. )e subparameters of the COP and lower extremities, and undertaking any exercise or usually reported in previous studies include position of the sports training programs were excluded. All volunteers were COP, root mean square (RMS) amplitude of the COP, total asked not to sleep less than 6 hours per night and not to use excursion of the COP, sway velocity of the COP, and sway medications or consume alcohol which would affect postural area of the COP. )e COP displacement (or the COP path stability control performance prior to participating in this length) and the COP velocity were suggested to be reliable study. In female volunteers, testing procedures were not conducted during their menstruation period or during and valid measures for determining postural stability control performance during standing [15, 18–21]. However, so- pregnancy. phisticated postural stability assessment instruments are high in cost, complexity, and time-consumption related to settings. Furthermore, most of them were often furnished in 2.2. Instruments and System Overview. )e SBAP (Figure 1) consisted of an acrylic platform (50 cm width x 50 cm research areas and could not be made easily accessible. )erefore, a number of studies have focused on developing length x 0.5 cm thickness) with four parallel beam load cells (each of 100 kg rated capacity, OEM) embedded under the accurate and reliable tools for determining postural stability control performance with lower cost equipment [22, 23]. In four corners of platform. )e load cells were connected with signal amplifiers (model Hx711) and a microcontroller the last decade, several studies demonstrated that a Wii TM Balance Board (WBB) with developed software was a (Arduino Uno). )e acrylic platform was mounted on an aluminium frame (50 cm width x 50 cm length x 15 cm valid and reliable tool for a low-cost postural stability control height) which was glued to a nonslip material on the bottom performance assessment [20, 22, 24–27]. )e WBB seemed surface. )e SBAP was interfaced with a laptop computer to be a suitable choice; however, the developed software (Lenovo Intel from previous studies is not widely disseminated. In addi- Core i5-8250U, CPU 1.6 GHz) via a USB tion, the cost of the WBB is quite high and is generally cable connector. )e weight of SBAP was approximately 7 kg. considered to be inaccessible in clinical settings and to the low-income population. )erefore, the current study aimed )e custom-made software for calculating the COP displacement and velocity was developed and written in to report the development of a low-cost, accurate, and re- liable posturography, evaluating COP time-domain pa- LabVIEW. )e COP displacement was referred to as a whole distance of the COP over the test duration (unit of mea- rameters. It was hypothesized that the developed posturography would display accurate measurement and surement: centimeter, cm). )e COP velocity was derived from the COP displacement over time (unit of measure- reliable test-retest reliability. )is low-cost posturography could offer easier access and more user friendly use in ment: centimeter per second; cm/second). )e signals from clinical settings. the four parallel beam load cells were delivered and con- verted to digital information by the written software. )e sampling frequency was recruited at 10 Hz by the software 2.Materials and Methods with no data filtering. )e signals from the load cells were processed and computed to get the total weight press on the )e current study utilized a cross-sectional research design platform along with the COP location (in the form of X and with test-retest reliability. A low-cost posturography was Y coordinates). )e COP displacements were calculated developed as a prototype named “Standing Balance As- from the total distance of change in the COP location over sessment Posturography (SBAP).” )e SBAP was pur- the testing duration. )e COP velocities were calculated posefully used to analyze the COP time-domain parameters from the COP displacement divided by the testing duration. (COP displacement and velocity) during standing. All After clicking the start button of the developed software, testing procedures were approved by the Naresuan Uni- SBAP started recording the input information for 40 seconds versity Institutional Review Board (IRB no. P10186/63). All and then stopped automatically. )e COP parameters were volunteers signed an informed consent before participating then processed and calculated during the middle 30 seconds. in the current study. )e COP displacement, the COP velocity, and a graphical real-time COP trajectory were presented on the laptop’s screen (Figure 2). 2.1. Participants. Participants were recruited in Naresuan University area through purposive sampling, using flyers, Before conducting postural stability control perfor- mance tests with SBAP, the accuracy of SBAP was initially posters, and personal contacts. )e number of participants (20 volunteers) was determined according to a guideline for tested with a standard 5 kg weight placed sequentially in nine positions over the platform (Figure 3). )e 5 kg weight was sample size estimation for analysis with the intraclass cor- relation coefficient (ICC) (two observations per subject, 90% placed 5 times repeatedly in each position. )e actual or true Journal of Aging Research 3 Load cell 1 Load cell 2 The SBAP Load cell 4 Load cell 3 (a) (b) Figure 1: )e standing balance assessment posturography (SBAP): (a) position of load cells; (b) overview of SBAP. Figure 2: Display of the developed software with SBAP. positions on the platform and the 45 calculated positions volunteers were asked to wear a comfortable shirt, short (9 positions x 5 times) from the software were then analyzed pants, and be bare foot. To prevent falling, volunteers wore a for the accuracy of the X and Y coordinates of the system. full body harness with nylon rope slings firmly suspended from the supporting frame. All volunteers were introduced to the testing protocols and were allowed to practice until 2.3. Data Collection. After volunteers had signed an in- they became familiar with the testing procedure. formed consent, they were screened according to the in- Postural stability control performance was tested via clusion and exclusion criteria. Volunteers who passed the standing balance assessments. )e standing balance as- criteria were tested for their dominant leg by performing sessments were varied visual inputs and bases of support to three activities: kicking a ball, writing their names on the challenge postural control ability. Standing balance assess- floor, and picking up an object. )e dominant leg was ments were tested in 6 different conditions, and each identified if they used the same leg to perform at least 2 condition was performed thrice. )e COP trajectory real- activities. time display was eliminated from volunteers during the tests. All measurements were conducted at a single site, the Successful trials were affirmed when the volunteer could Faculty of Allied Health Sciences, Naresuan University, stand without swaying or falling and did not open their eyes )ailand. )e laboratory room was silent and no other during the eyes closed condition. If an unsuccessful trial activities were allowed to avoid distraction. Initially, occurred, the volunteer was asked to perform repeatedly 4 Journal of Aging Research 2.4. Statistical Analysis 2.4.1. Accuracy of SBAP. )e mean differences between the true and calculated X and Y coordinates from the nine positions over the platform (N � 45) were determined for accuracy using an intraclass correlation coefficient (two-way random, absolute agreement, single measure) [29] and a standard error of measurement (SEM). )e SEM was ana- lyzed using the equation “SEM � SD (square root of 1- ICC)” [25, 30]. 2.4.2. Test-Retest Reliability of SBAP during Postural Stability Control Performance Tests in Six Conditions. )e charac- teristics of volunteers were descriptively reported. )e mean of the COP displacements and the COP velocities during the six testing conditions in session 1 and 2 were descriptively demonstrated. Scatter plots were primarily checked for Figure 3: Nine positions and a 5 kg weight for testing SBAP linearity of COP displacements and velocities between accuracy. session 1 and 2. Afterward, test-retest reliability of the postural stability tests with SBAP were analyzed from dif- ferent days (sessions 1 and 2) using the intraclass correlation until 3 successful trials in each condition were completed. coefficient (ICC) (two-way mixed effect, consistency, aver- )e 6 different standing postural stability control perfor- age measure). )e values of the ICC were qualitatively mance test conditions were as follows (Figure 4). classified as displaying excellent (ICC >0.90), good (ICC (i) Double leg stance with feet shoulder width apart between 0.75 and 0.90), moderate (0.50–0.75), and poor and eyes open (DLS-SW-EO), arms by their sides, (ICC <0.50) reliability [31]. Additionally, a coefficient of the distance between feet was recorded variation (CV) [30] and SEM of the COP displacement and velocity in sessions 1 and 2 were also analyzed. Furthermore, (ii) Double leg stance with feet shoulder width apart Bland–Altman plots for the COP displacements and ve- and eyes closed (DLS-SW-EC), arms by their sides, locities were also graphically displayed showing the agree- the distance between feet was recorded ment and systematic bias of each measurement between (iii) Double leg stance with feet together and eyes open sessions with 95% limits of agreement (LOA). Statistical (DLS-FT-EO), arms by their sides analysis was conducted with the Statistical Package for Social (iv) Double leg stance with feet together and eyes closed Sciences (SPSS). )e p value was set at or less than 0.05 for all (DLS-FT-EC), arms by their sides statistical analyses. (v) Single leg stance with eyes open (SLS-EO), other leg bent at 90 degrees of knee flexion toward the back, 3.Results arms crossed on their chest 3.1. Volunteers. Twenty young adult volunteers (age � (vi) Single leg stance with eyes closed (SLS-EC), other 21.45± 0.59 years, weight � 53.21± 7.32, height � 165.50± leg bent at 90 degrees of knee flexion toward the 5.16 cm, and body mass index � 19.40± 2.34 kg/m ) were back, arms crossed on their chest recruited in the current study. All volunteers were com- )e testing conditions were randomly assigned for each pletely measured against the testing protocols in sessions 1 volunteer. )e volunteers were asked to stand still in the and 2. Physical and emotional changes which apparently middle of SBAP for over 40 seconds in each test. Two disturbed postural stability control performance were not minutes rest or longer was allowed between trials or until the observed in all volunteers. No falling or serious adverse volunteers had no fatigue or tiredness before starting the effects were detected throughout the study. new trial or condition. )e SBAP was set at zero shift before collecting data in each trial. All testing procedures were performed twice with identical procedures for all volunteers 3.2. Accuracy of SBAP. Means and standard deviations of the in two different sessions. )e second session was tested 24 differences between the true and calculated X and Y coor- hours after the first session. Each session took place over dinates were −0.13± 0.22 cm and −0.12± 0.17 cm, respec- approximately 45 minutes. All measurements in the two tively. )e reliability coefficients from ICC analysis were 0.99 sessions were conducted by the same tester who was ap- (95% confidence interval � 0.99–1.00, p< 0.001) for both X propriately instructed and trained in all testing protocols. )e and Y coordinates. )e SEMs of differences between true tester separately recorded and exported the testing parameters and calculated positions of X and Y coordinates were of individual volunteers after completing the testing proce- 0.022 cm and 0.017 cm, respectively. )ese results demon- dures in each session. All testing parameters were then an- strated high accuracy of SBAP to estimate the X and Y alyzed with statistical software by another researcher. coordinates on platform. Journal of Aging Research 5 (a) (b) (c) Figure 4: Standing postural stability control tests: (a) double leg stance with feet shoulder width apart, (b) double leg stance with feet together, and (c) single leg stance. 3.3. Test-Retest Reliability of the Postural Stability Control COP displacements and velocities between session 1 and 2 in six testing conditions was demonstrated via Bland–Altman Performance Test with SBAP in Six Conditions. Scatter plots of both the COP displacement and velocities in six testing plots with LOAs (Figures 7 and 8). )ere were no obvious conditions showed the linearity relationships of parameters trends or systematic bias between the measurements in all between sessions 1 and 2 (Figures 5 and 6). Means and testing conditions. standard deviations (SD) of the COP displacements and velocities in both sessions are demonstrated in Table 1. )e 4.Discussion results of the test-retest reliability of the postural stability control performance test with SBAP between sessions 1 and In the study of reliability analysis, measurement errors can 2, expressed with ICC values, are given in Table 2. )e results be attributed to three sources including rater, measuring showed moderate to high test-retest reliability between instrument, and variability of the characteristics being sessions 1 and 2 in the six different conditions. A moderate measured [31]. Measurement errors were minimized by test-retest reliability was found with the COP displacement suitably designing the testing procedures and protocols. All and velocity in the double leg stance with feet shoulder width measurements of testing protocols in the two sessions were apart and eyes open condition. A good test-retest reliability conducted by the same well-trained tester with a clear was identified with the COP displacements and velocities in procedure of testing protocols in order to control the the double leg stance with feet shoulder width apart and eyes measurement error from the rater. )e tested parameters of closed, double leg stance with feet together and eyes closed, individual volunteers were separately processed and and single leg stance with eyes open conditions. An excellent exported after completing each session. Afterward, the tested reliability was expressed with the COP displacement and parameters were analyzed by another researcher to reduce velocity in the double leg stance with feet together and eyes the rater’s bias on data analyses. For eliminating the mea- open and single leg stance with eyes closed conditions. surement error from measuring instrument, the low-cost )e CV and SEM of the COP displacements and ve- posturography (SBAP) was initially tested for its accuracy by locities in both sessions during the 6 testing conditions are analyzing the differences between true and calculated X and reported in Table 3. In both sessions, the CV of the COP Y coordinates before testing test-retest reliability in the displacements ranged 17.92–25.77%, whereas the CV of the young adult volunteers. )e results of this study demon- COP velocities ranged 18.09–27.69%. In each testing con- strated that SBAP had excellent precision of calculated X, Y dition, consistent CV values were observed between sessions coordinates (ICC � 0.99, SEM <0.03 cm) when compared 1 and 2 for both the COP displacement and velocity. with the true positions on the platform. )e protocols for )e SEM values were increased according to the level of postural control performance testing were appropriately difficulty of the testing conditions (from the easiest, con- designed as recommend by previous studies, including foot dition 1, to the hardest, condition 6). Again, the SEM values and leg positions, testing duration, repetitions of testing, were consistently observed between sessions 1 and 2 for both visual acuity conditions, and random-order of the testing the COP displacement and velocity. )e agreement of the conditions [15, 18, 32, 33], in order to control the variability 6 Journal of Aging Research cm cm 40 50 cm cm 0 0 0 5 10152025 0152 10 5 20530 COP displacement in session 1 COP displacement in session 1 (a) (b) cm cm 50 100 30 60 20 40 10 20 cm cm 0 0 0 10 203040 0 10 2030405060 COP displacement in session 1 COP displacement in session 1 (c) (d) cm cm 100 250 80 200 60 150 40 100 20 50 cm cm 0 0 0 20 40 60 80 100 0 50 100 150 200 250 COP displacement in session 1 COP displacement in session 1 (e) (f) Figure 5: Scatter plots of COP displacements between sessions 1 and 2 from six testing conditions. (a) COP displacements during DLS-SW- EO. (b) COP displacements during DLS-SW-EC. (c) COP displacements during DLS-FT-EO. (d) COP displacements during DLS-FT-EC. (e) COP displacements during SLS-EO. (f) COP displacements during SLS-EC. between sessions. Hence, the results of reliability analyses according to the difficulty of the tests, from the wider base of support (BOS) with the presence of visual input to the will mostly reflect the consistency of the postural stability control performance testing with SBAP. steeper BOS and the absence of visual input. It was suggested In the current study, only one group of volunteers was that as the COP displacement and velocity increased, more measured twice for COP displacements and velocities. postural stability was needed during quiet standing [21]. Young healthy adult volunteers who had no significant However, this concept might not be implied for all situa- physical factors affecting postural stability control perfor- tions. Palmieri and colleagues [18] elucidated that COP mance were recruited (both males and females in equal displacement and velocity alone might not adequately ex- number). All volunteers were asked to sleep sufficiently and plain the nature of postural stability control. )erefore, other not to use medications or alcohol which would affect pos- parameters of the COP domain should be considered for postural stability control. Additionally, various factors af- tural stability control prior to joining the testing protocols throughout the study. )e interval durations between ses- fected the characteristics of postural stability control, such as sions 1 and 2 of all volunteers were approximately 24-hour testing conditions, testing protocol, assessment tools, and apart. Female volunteers were not tested if they were in the characteristics of subjects. As mentioned, the COP dis- menstruation period or pregnant. As mentioned above, the placement and velocity may be better appropriated for in- variability of the measurement scores caused by being tested dividual longitudinal monitoring. participants would be probably controlled. )e gradual increases of the standard deviations of COP From testing conditions 1−6, the values of the COP displacements and velocities were similarly observed in both displacement were gradually increased. )ese increasing sessions. )is implies that the variability of the COP dis- values were also observed with the values of the COP ve- placements and velocities increases as the difficulty of testing locity. )e testing conditions were purposefully ranked protocols increases (from testing conditions 1–6). However, COP displacement COP displacement COP displacement in session 2 in session 2 in session 2 COP displacement COP displacement COP displacement in session 2 in session 2 in session 2 Journal of Aging Research 7 cm cm 1.4 1.2 1.5 0.8 0.6 0.4 0.5 0.2 cm cm 0 0 0 0.2 0.4 0.6 0.8 0 0.2 0.4 0.6 0.8 1 COP velocity in session 1 COP velocity in session 1 (a) (b) cm cm 2 3 2.5 1.5 1 1.5 0.5 0.5 cm cm 0 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 0.5 1 1.5 2 COP velocity in session 1 COP velocity in session 1 (c) (d) cm cm 4 8 3.5 7 3 6 2.5 5 2 4 1.5 1 2 0.5 1 cm cm 0 0 0 2 46 8 0 0.5 1 1.5 2 2.5 3 3.5 COP velocity in session 1 COP velocity in session 1 (e) (f) Figure 6: Scatter plots of COP velocities between sessions 1 and 2 from six testing conditions. (a) COP velocity during DLS-SW-EO. (b) COP velocity during DLS-SW-EC. (c) COP velocity during DLS-FT-EO. (d) COP velocity during DLS-FT-EC. (e) COP velocity during SLS-EO. (f ) COP velocity during SLS-EC. Table 1: Means and standard deviations of COP displacements and velocities of six conditions in sessions 1 and 2. COP displacements COP velocities Conditions Session 1 Session 2 Session 1 Session 2 (cm) (cm) (cm/second) (cm/second) Double leg stance with feet shoulder width apart and eyes open 15.06± 3.42 15.04± 3.33 0.50± 0.11 0.50± 0.11 Double leg stance with feet shoulder width apart and eyes closed 18.21± 3.73 19.54± 3.98 0.61± 0.12 0.65± 0.13 Double leg stance with feet together and eyes open 25.18± 5.56 24.49± 4.86 0.84± 0.19 0.82± 0.16 Double leg stance with feet together and eyes closed 38.01± 8.29 39.43± 10.16 1.27± 0.28 1.30± 0.36 Single leg stance with eyes open 58.39± 13.55 56.31± 10.09 1.95± 0.45 1.88± 0.34 Single leg stance with eyes closed 132.21± 28.39 134.17± 29.23 4.41± 0.95 4.47± 0.97 most values of CVs of COP displacements and velocities in all testing conditions for both the COP displacement and all testing conditions and sessions seem to be consistent velocity was good, as demonstrated in the Bland–Altman across testing conditions and sessions (most of CV values plots and LOAs. Most differences between the 2 sessions of were 20–30%). )erefore, it could be stated that the in- COP measurement with SBAP were within ±2 SD of the creased variability observed depended on the inherent dif- mean differences in both positive and negative directions. ficulty of the testing conditions. )e test-retest reliabilities of )is indicated no significant bias between the measurements static postural control tests for both the COP displacement with SBAP from different sessions. Additionally, the values and velocity of SBAP were moderate to excellent. )e SEM of the average COP displacement and velocity were con- values of all measurements in this study were acceptable (less sistent between sessions and was in a similar range to those than 30%) [19, 32]. )e agreement between measurements in from studies which evaluated the postural control COP velocity in session 2 COP velocity in session 2 COP velocity in session 2 COP velocity in session 2 COP velocity in session 2 COP velocity in session 2 8 Journal of Aging Research Table 2: Results of test-retest reliability (intraclass correlation coefficients) for COP displacements and velocities between sessions 1 and 2 in six conditions. COP displacements COP velocities Conditions Reliability coefficients Reliability coefficients P value P value (95% confidence interval) (95% confidence interval) Double leg stance with feet shoulder ∗ ∗ 0.62 (0.05, 0.85) 0.02 0.62 (0.05, 0.85) 0.02 width apart and eyes open Double leg stance with feet shoulder ∗ ∗ 0.85 (0.61, 0.94) <0.001 0.85 (0.61, 0.94) <0.001 width apart and eyes closed Double leg stance with ∗ ∗ 0.91 (0.76, 0.96) <0.001 0.91 (0.76, 0.96) <0.001 feet together and eyes open Double leg stance with feet ∗ ∗ 0.78 (0.44, 0.91) 0.001 0.78 (0.44, 0.91) 0.001 together and eyes closed Single leg stance with ∗ ∗ 0.83 (0.56, 0.93) <0.001 0.82 (0.56, 0.93) <0.001 eyes open Single leg stance ∗ ∗ 0.91 (0.76, 0.96) <0.001 0.91 (0.76, 0.96) <0.001 with eyes closed Statistical significant at p< 0.05. Table 3: Results of coefficients of variation (CV) and standard errors of measurement (SEM) of COP displacements (cm) and COP velocities (cm/second) of six conditions in sessions 1 and 2. COP displacements COP velocities Conditions Session 1 Session 2 Session 1 Session 2 CV (%) SEM CV (%) SEM CV (%) SEM CV (%) SEM Double leg stance with feet shoulder width apart and eyes open 22.71 2.11 22.14 2.05 22.00 0.07 22.00 0.07 Double leg stance with feet shoulder width apart and eyes closed 20.48 1.44 20.37 1.54 19.67 0.05 20.00 0.05 Double leg stance with feet together and eyes open 22.08 1.67 19.84 1.46 22.62 0.06 19.51 0.05 Double leg stance with feet together and eyes closed 21.81 3.89 25.77 4.77 22.05 0.13 27.69 0.17 Single leg stance with eyes open 23.21 5.59 17.92 4.16 23.08 0.19 18.09 0.14 Single leg stance with eyes closed 21.47 8.52 21.79 8.77 21.54 0.29 21.70 0.29 performance during standing with the WBB and a labora- calculation of the written software were not precisely tory-grade force platform [16, 19, 20, 25, 34], eventhough explained. Nowadays, the WBB has decreased in popularity, there were some discrepancies in testing parameters when and eventhough the cost of the WBB has also decreased compared to this study. )erefore, it could be stated that the somewhat, its cost remains high for extensive use in clinical settings or even in home use. However, the pressure sensors developed low-cost posturography in this study had enough reliability for assessing postural stability control perfor- used in SBAP are currently decreasing in price and mance during standing. are convenient in that they can be connected to various )e instrumented test for postural stability control computer programs to effectively create the software for performance is suggested to be better than the clinical tests, biomechanical analysis. )erefore, we decided to develop a reporting more accurate and precise scores and providing low-cost posturography using simple load cells and plat- more details related to biomechanical parameters. None- form. In future developments of the system, it would be theless, the instrumented tests have rarely been used in possible to lower the cost of production and the weight of clinical settings due to their difficulty of setup, heavy weight, SBAP. and high cost. A number of studies have investigated the )e limitations of this study were related to materials reliability and validity of a low-cost posturography and external validity. )e load cells were limited to 100 kg TM loaded. )e sampling rate was low (10 Hz) with no data [16, 20, 22, 24–27]. )ey proposed the Wii Balance Board (WBB) as a low-cost posturography, which had moderate to filtering, whereas previous studies used at least 40 Hz (for the WBB) or up to 200 Hz (for a laboratory-grade force excellent reliability and good validity in comparison with a laboratory-grade force platform. However, some technical platform) with low-pass filtering (less than 10 Hz) limitations of the WBB were reported, including an in- [15, 16, 20, 22, 24–27, 32]. However, the results of the consistent sampling rate and a poor signal to noise ratio, recorded parameters still had sufficient reliability and were which may have impacted the analysis of the COP pa- consistent with previous studies [16, 19, 20, 25, 34]. Vol- rameters [22]. Consequently, several studies tried to address unteers in this study were symptom-free individuals, so the those limitations by improving the input signals with results could not be referred to another population. low-pass filtering to attenuate noise [16, 20, 22, 24–27]; In future studies, the accuracy of posturography should however, the technical details related to data acquisition and be tested with various weights and numbers of X and Y Journal of Aging Research 9 10 10 7.12 +1.96 SD 4.34 +1.96 SD 5 5 Mean difference Mean difference 0.02 0 0 0 5 101520253035 0.00 5.00 10.00 15.00 20.00 25.00 –1.33 –5 –5 –7.00 –7.07 –1.96 SD –1.96 SD –10 –10 Average COP displacements from two sessions (cm) Average COP displacements from two sessions (cm) (a) (b) 10 30 6.89 +1.96 SD 14.47 +1.96 SD 0.69 Mean difference Mean difference –1.42 0 0 0 10 20 30 40 –5 5 152535455565 –10 –5.51 –5 –20 –1.96 SD –17.31 –1.96 SD –10 –30 Average COP displacements from two sessions (cm) Average COP displacements from two sessions (cm) (c) (d) 30 50 20.64 +1.96 SD 32.13 +1.96 SD 2.07 Mean difference –1.96 Mean difference 0 20 40 60 80 100 0 5 100 150 200 250 –10 –10 –30 –16.49 –1.96 SD –20 –1.96 SD –36.06 –30 –50 Average COP displacements from two sessions (cm) Average COP displacements from two sessions (cm) (e) (f) Figure 7: Bland–Altman plots and limits of agreements (LOAs) of COP displacements in sessions 1 and 2 in six testing conditions. (a) COP displacements during DLS-SW-EO. (b) COP displacements during DLS-SW-EC. (c) COP displacements during DLS-FT-EO. (d) COP displacements during DLS-FT-EC. (e) COP displacements during SLS-EO. (f) COP displacements during SLS-EC. 0.4 0.4 0.24 +1.96 SD 0.14 0.2 0.2 +1.96 SD 0.001 Mean difference Mean difference 0 0 0 0.2 0.4 0.6 0.8 1 1.2 0 0.2 0.4 0.6 0.8 –0.05 –0.2 –0.24 –0.2 –0.23 –1.96 SD –1.96 SD –0.4 –0.4 Average COP velocities from two sessions Average COP velocities from two sessions (cm/second) (cm/second) (a) (b) Figure 8: Continued. Differences in COP Differences in COP Differences in COP Differences in COP velocity displacement (cm) displacement (cm) displacement (cm) (cm/second) Differences in COP velocity Differences in COP Differences in COP Differences in COP (cm/second) displacement (cm) displacement (cm) displacement (cm) 10 Journal of Aging Research 0.4 1 0.23 +1.96 SD 0.52 +1.96 SD 0.2 0.5 0.02 Mean difference Mean difference –0.03 0 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 0.5 1 1.5 2 2.5 –0.58 –0.2 –0.5 –0.19 –1.96 SD –1.96 SD –0.4 –1 Average COP velocities from two sessions Average COP velocities from two sessions (cm/second) (cm/second) (c) (d) 1 2 0.69 +1.96 SD 1.07 +1.96 SD 0.5 1 0.07 Mean difference Mean difference –0.07 0 0 0 0.5 1 1.5 2 2.5 3 3.5 0 2 46 810 –0.55 –1.20 –0.5 –1 –1.96 SD –1.96 SD –1 –2 Average COP velocities from two sessions Average COP velocities from two sessions (cm/second) (cm/second) (e) (f) Figure 8: Bland–Altman plots and limits of agreements (LOAs) of COP velocities in sessions 1 and 2 in six testing conditions. 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Journal

Journal of Aging ResearchHindawi Publishing Corporation

Published: Aug 5, 2021

References